Test flattened below, gently domed above to flat apical disc.
Apical disc thick forming raised platform; dicyclic; plates firmly bound to corona. Genital plates pentagonal; gonopore at outer interradial point bounded by interambulacral zones; inner edge sunken, forming a periproctal ledge. Ocular plates smaller and projecting. Smooth other than for a single perianal tubercle developed on the inner edge of genital plates which is sunken. Periproct relatively small and subpentagonal.
Ambulacra straight; pore-pairs small, uniserial; slightly larger on apical surface, the two pores separated by a raised interporal knob; ambulacra expanded orally into phyllodes.
Ambulacral plating in triads throughout, with goniopygid-style compounding; two unequal elements extending to the perradial suture and united by the primary tubercle, plus a third small demiplate in each triad.
Interambulacral plates a little wider than tall; with a large primary tubercle on each; secondary tubercles and miliary granulation generally sparse and no scrobicular ring. Primary tubercles largest just above ambitus.
Tubercles imperforate and non-crenulate, with no surrounding platform.
Basicoronal interambulacral absent; no sphaeridial pits.
Peristome subcircular, slightly sunken; buccal notches sharp with raised rim; no tag.
Spines relatively short (less than test diameter); stout shaft, with cortical layer in outer part which is often finely ribbed; angular in cross section.
G. arabicus Smith, 1995; Maastrichtian, United Arab Emirates.
G. arnaudi Cotteau, 1883; Turonian, France.
G. brossardi Coquand in Cotteau, 1865; Cenomanian, Tunisia.
G. conicus Peron & Gauthier; Cenomanian, Algeria.
G. coquandi Cotteau, 1865; Cenomanian, Algeria.
G. coutini Lambert, 1931; Turonian, Algeria.
G. decoratus Desor, 1855; Valanginian, France.
G. delphinensis Gras, 1848; Barremian-Aptian, France, England, Spain [includes G. noguesi Cotteau, 1863].
G. durandi Peron & Gauthier, 1881; Santonian, Algeria.
G. heberti Cotteau, 1866; Danian, Belgium and The Netherlands.
G. impressus Peron & Gauthier, 1879; Cenomanian, Algeria.
G. innesi Gauthier, 1901; Santonian, Egypt.
G. intricatus Agassiz, 1838; Valanginian-Hauterivian, France.
G. loryi Cotteau, 1865; Lower Aptian, France.
G. major Agassiz, 1838; Cenomanian, France.
G. marticensis Cotteau, 1865; Santonian, France.
G. menardi Desmarest, 1825; Upper Albian-Cenomanian, western Europe.
G. meslei Peron & Gauthier, 1879; Cenomanian, Algeria.
G. messauod Peron & Gauthier, 1879; Cenomanian, Algeria.
G. minor Sorignet, 1850; Palaeocene, western Europe.
G. peltatus (Agassiz, 1836); Barremian-Aptian, France.
G. peroni Thomas & Gauthier, 1889; Upper Cenomanian, Tunisia.
G. pilleti Cotteau, 1883; Tithonian, France.
G. royanus d\'Archiac, 1851; Campanian, France.
G. superbus Cotteau & Gauthier, 1895; Campanian-Maastrichtian, Iraq, Saudi Arabia. [see Smith 1995]
G. tetraphyma Lambert, 1907: Maastrichtian, Spain.
G. whitei (de Loriol, in White 1887); Palaeocene, Brasil.
G. whitneyi Smith & Rader, 2009; Albian, Texas, USA
G. sp. Smith & Rader, 2009; Lower Albian, USA, Europe
The sunken periapical tubercles and smooth unornamented apical disc plates distinguish this from all other Acropeltidae.
Agassiz, L. 1838. Monographies d'Échinodermes vivants et fossiles. Première monographie: Des Salénies. Petitpierre, Neuchâtel, 32 pp., 5 pls.
Jagt, J. W. M. 2000. Late Cretaceous-Early Palaeogene echinoderms and the K/T boundary in the southeast Netherlands and northeast Belgium. Part 4:Echinoids. Scripta Geologica 121, 181-375.
Mortensen, T. 1935. A monograph of the Echinoidea II. Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C. A. Reitzel, Copenhagen.
Smith, A. B. 1995. Late Campanian- Maastrichtian echinoids from the United Arab Emirates-Oman border region. Bulletin of the Natural History Museum, London (Geology Series) 51, 121-240.